/Engine/Source/Runtime/Core/Public/Serialization/PackageWriter.h
Load the bytes of the previously-cooked package, used for diffing
virtual bool GetPreviousCookedBytes ( const [FPackageInfo](API\Runtime\Core\Serialization\IPackageWriter\FPackageInfo) & Info, [FPreviousCookedBytesData](API\Runtime\Core\Serialization\ICookedPackageWriter\FPreviousCookedBytesData) & OutData )